Filament winding of complicated shapes is carried out by depositing a strand under tension in the cavities of a mold designed to hold the deposited strand in the desired shape. The strand is wrapped around and around the same cavities of the mold until the desired thickness of strand is deposited. Usually the strand is completely wetted out with a binder before it is wound into the cavities of the mold, but the invention is not limited in this respect. As the binder wetted strand is pulled down into the mold, excess binder exudes into the spaces between the wrappings of the strand and also into contact with the surfaces of the mold. The binder is then caused to harden in the mold to bind the fibers together and hold them in the desired shape. Binders will usually stick to the surface of the mold, and the art has long mitigated the mold sticking problem by incorporating mold release agents into the binders. The mold release agents appear to function by rising to the external surfaces of the binder as it agglomerates, to thereby coat the surface of the mold.
Another problem which occurs in the filament winding art, is that it is impractical for the most part, to incorporate fibers crosswise to the windings for the purpose of binding the windings together. Separation of the windings therefore is prevented almost entirely by the binder, and its attachment to the filaments of the strand. For this reason, the strength of the binder may be more critical in filament wound parts than in other types of fiber reinforced parts.
A still further problem exists in the process of filament winding in that the molds are usually rotated while a "finger" positions the strand in the proper location relative to the mold's cavities. The tension on the binder wetted strand, in conjunction with the rotation of the mold, causes excess binder to flow out of the mold cavities over other surfaces of the mold, including its separating and clamping surfaces. This excess resin has proved costly to remove.
Also in the commercial production of filament wound parts, a considerable time period is spent winding the strand into the cavities of the mold. To achieve volume production, therefore, it is necessary to have a large number of such molds, not only for the winding operation, but to support the wound part during the time that the binder is hardening. In the case where the binder is a thermosetting resin, the mold with a wound part therein is moved to an oven and heated to approximately 350.degree. F. to cause the binder to harden. During this time, another mold will have been placed in the winding machine and another part formed. The molds are usually made of a cast aluminum, or other metal, to withstand the temperature and handling; and the cost of producing and machining the complicated shapes of the mold is appreciable.